1. Field of the Invention
The present invention relates to a white opaque film, and in particular relates to an oriented white opaque polyester film.
2. Description of the Related Art
A cavitation additive is added into a polyester film, and the polyester film is stretched by a uniaxial or a biaxial stretching process to form large fine voids in the polyester film. Following, a white polyester film having good whiteness and good opacity is obtained. A polyester film itself has high surface tension and high temperature resistance, thus, a polyester film is suitable for the printing, transcription and synthetic paper labeling fields, such as the packaging, building material, and commercial printing industries.
U.S. Pat. No. 5,672,409 discloses a biaxially oriented white polyester film which comprises poly(ethylene terephthalate) (PET) and a cavitation additive, wherein the cavitation additive comprises about 5-25 wt % of inorganic particles and 2-25 wt % of the polyolefin.
U.S. Pat. No. 6,326,431 discloses a biaxially oriented white polyester film which comprises poly(ethylene terephthalate) (PET) and a cavitation additive, wherein the cavitation additive comprises cyclic olefin copolymer.
However, when the inorganic particles are used as the cavitation additive, the inorganic particles are not easily dispersed well and may cause a dust pollution problem. Additionally, when the films are slitted during converting, the inorganic particles may cause slitting blade wear problems.
Accordingly, there is a need to develop an oriented white opaque polyester film, wherein the cavitation additive is dispersed well in the polyester film, and the dust pollution problem is avoided.